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E. R. STONE GRATE STRUCTURE Dec. 1, 1936.

Filed Aug. 28, 1934 3 Sheets-Sheet 1 FIG-21.1.

- INVENTOR EARLLRbToNE.

- BY awn, ATTORNEY Dec.1,1936. R; NE 2,062,481

GRATE STRUCTURE v Filed Aug. 28, 19:54 IS SheetS-Sheet 2 \IHIMIIIIHIMIM-HIIIUHIIIIHIM All I llllllllllllllfl INVENTOR WITNESSES:

7 BY 75 --M (g ATTORNEY ,3 EARLLRSTONE Dec. 1, 1936.

E. R/STONE GRATE STRUCTURE s Sheets- Sheet :5

Filed Aug. 28, 1934 i I INVENTOR EHRLL. E. STONE wqspvawq ATTORNEYPatented Dec. 1, 1936 UNITED STATES QRATE STRUCTURE Earll R. Stone,Lansdowne, Pa., assignor to Westinghouse Electric & ManufacturingCompany, East Pittsburgh, Pa., a corporation of Pennsylvania ApplicationAugust 28, 1934, Serial No. 741,772

4 Claims.

My invention relates to fuel-supporting structure for combustionapparatus and it has for an object to provide for improved air admissionwith variable conditions of the fuel bed.

5 Heretofore, the fuel-burning grate of combustion apparatus hasfrequently consisted of fuelsupporting members with holes extendingtherethrough or therebetween for the admission of air into the fuel bedfor supporting combustion. The 10 draft, in natural draft furnaces, orthe air pressure, in forced draft apparatus, causes flow of air throughsuch holes and through the fuelbed.

Usually, the holes have been either straight or slightly tapered, theresistance to flow of air increasing as the holesare decreased in size.In any fuel bed, it is well known that the resistance to flow, or dropin pressure through the fuel bed is not uniform throughout its area andheretofore the straight or tapered holes or passages 30 have ofiered butlittle change in pressure drop with increased flow, in consequence ofwhich the sections of the fuel bed, which offer decreased resistance toflow, either because of the character or thinness of that section of thefuel bed, 25 would be supplied with an excess amount of air, therebyincreasing the combustion rate in such sections and resulting in burningout ofthe fuel bed on such sections relatively'faster than on othersections,

In order to overcome the aforementioned irregularity in combustion,grates with pin holes have been used. However, the holes are usually sosmall that high resistance to air fiow therethrough results, therebymaking the pressure drop through the holes the predominating resistance.In other words, the holes'being of small area, the pressure drop throughthe grate is large compared to that of the fuel bed and variation incharacter or thickness of the fuel bed have but little effect on airfiow. With this type of grate, in order to secure necessary air flowhigher differential pressures are required, making it essential toprovide higher stacks, or, in the case of forced draft, larger blowersand increased 0 power for driving the latter.

In accordance with my invention, I provide a fuel-supporting structurewherein the air pas sages are constructed and arranged to give avariable resistance. to air flow therethrough with- 0 out the necessityof providing high differential pressures. This and other advantages areobtained by having the elements forming the fuelsupporting surfacesprovided with means of securing a series of orificesin each air passagewith chambers between adjacent orifices, the air passing through theorifices at high velocities and having the velocity energy largelytransformed into static pressure in the chambers following the orifices.

In order that air may be sufiicient for suppo'rting combustion, theremust be enough pressure difference between the space underneath thegrate and the space above the fuel bed to overcome resistance to airfiow through the air passages of thegrate and through the fuel bed. 10Ordinarily, the grate air passages offer little resistance, with theresult that irregularities in fuel bed resistance may cause undesiredirregularities in air fiow. For example, excess flow may occur in aregion of small fuel bed resistance, thereby l5 increasing thecombustion rate at such region and bringing about lessened pressuredifference and consequent lessened flow through regions having greaterfuel bed resistance. As hereinbefore already pointed out, an attempt tomeet this objection has been made by providing very small air passages,but such small air passages are undesirable because of the consequenthigh pressure required to secure necessary air flow. It is well knownthat the-flow through an orifice is a function of the square root of thepressure difference across the orifice. Accordingly, instead ofaccomplishing increased resistance to air flow through a grate providedwith relatively small passages, I provide a labyrinthine arrangementconsisting of orifices with chambers between adjacent orifices. In otherwords, I provide for abrupt changes in area of flowfrom a chamber to anorifice and vice versa in each passage, the eflect of the abrupt flowarea being to decrease the quantity of air flowing compared to a plainpassage. The air has maximum velocities through the orifices, but, dueto abrupt changes in area, large losses occur incident to changes ofvelocity energy into. pressure energy and 4 vice versa, and alsodefinite energy losses due to conversions, with the result that, shouldthere be a decrease in resistance at the discharge end of the passage,such decrease is compensated for by the increased effective resistanceof the passage with very little increase inflow therethrough. Thisarrangement of orifices with chambers between adjacent orifices in theair passage causes the flow to increase at a lesser rate in case ofdiminishing fuel bed resistance than with, other types of air admittinggrates. In other words, in accordance with my invention, grateresistance to air flow due to the losses from the changes in airvelocity in passing through the alternate orifices and chambers isincreased thus producing a choking effect against excessive air fiowwithout substantially increasing the air pressure required to secure thenormal fiow. This choking effect increases the grate resistance to airfiow and tends to counteract the lower pressure drop through sections ofthe fuel bed of low resistance. This arrangement of air passage is moreeffective than the ordinary grate in equalizing the rate of air fiowthrough the various sections of high and low resistance in the fuel bed,thus securing more uniform combustion over the entire fuel bed area.

Accordingly, it is a more specific object of my invention to provide theair admitting passages of grate members each with a series of orificesand chambers between adjacent orifices, this arrangement functioning toprevent substantial irregularities of combustion with irregularities infuel bed resistance.

These and other objects are effected by my invention, as will beapparent from the following description and claims taken in connectionwith the accompanying drawings, forming a part of this application, inwhich:

Fig. 1 is a transverse sectional view of a single retort stoker havingmy improvement applied thereto;

Fig. 2 is a sectional view taken along the line II-H of Fig. 1;

Fig. 3 is a fragmentary view of a chain grate having my improvementapplied thereto.

Fig. 4 is a fragmentary detail view showing my improvement applied totuyre plates of an underfeed stoker;

Fig. 5 is a bottom plan view of one of the tuyere plates shown in Fig.4;

Figs. 6 and '7 show a further embodiment of the improvement applied totuyre plates;

Figs. 8 and 9 are detail views of stoker grate bar elements embodying asecond form of my invention;

Figs. 10 and 11 are sections taken along the lines X-X and XI-XI,respectively, of Fig. 9:

Fig. 12 is a view similar to Fig. 8 and showing a modified mode ofsecuring variation in air fiow; Figs. 13, 14, and 15 are sectional viewstaken along the lines X[IIXI1I, IUVXIV, and XVXV, respectively, of Fig.12;

Fig. 16 is a fragmentary view of a tuyre plate incorporating the secondform of my invention; 'm

Figs. 17, 18, and 19 are detail views of side-wall tuyres incorporatingmy improvements, Fig. 19 being a sectional view taken along the linesXIXX[X of Fig. 18.

Referring now to the drawings more in detail, in Fig. 1, I show astructure including a retort, at l0, having sets of grate bars llextending laterally therefrom, this being a well-known type of singleretort underfeed stoker and which necessitates no further description indetail.

As is well known, fuel is supplied to the retort and fiows laterallyover either side thereof onto the grate bars I I, the fuel advancingdownwardly on the grate bars at either side of the retort and beingconsumed.

' Air for the combustion of fuel flows through the grates and fuel beddue to the pressure difference existing between the space I2 below thestructure and the space l3 in the combustion chamber.

In order that a choking effect may be secured in the air passagesbetween adjacent grate bars I I, in Figs. 1 and 2, I show the barsprovided with ribs l4, l5, l3, and I! cooperating to provide first,second, third and fourth stage orifices l8, I9, 20, and 2| with chambers22, 23, and 24 between adjacent orifices l8 and l9, l9 and 20, and and2|, respectively, it being understood that, any suitable number oforifices arranged in series may be provided. In these figures, as wellas the others hereinafter described, each air passage consists of one ormore chambers and orifices leading to and from each chamber. Thisarrangement provides for 'abrupt changes in flow area where the orificesand chambers connect. The abrupt change in area is productive ofinefficient conversion of velocity energy into pressure energy and viceversa and the effect thereof is to reduce the quantity of air dischargedcompared to a plain passage. With passages of this type, if the fuel bedis uneven, or if the resistance thereof varies, the differences in airfiow that would otherwise be induced by such variation tends to beequalized by the effect of the passages. While a decrease in resistanceat the discharge end of a passage tends to increase the flow of airthrough the passage, because, of the abrupt area changes and consequentinefficient energy conversions, very little increase in fiow is requiredto compensate for the diminished resistance. Accordingly, with myimproved grate surface, the tendency of air to fiow through thin places,or places of lesser resistance, with an undesirable loss in air andimpaired combustion efficiency is overcome. With my arrangement,

. due to the inherent choking effect of each passage, variations in fuelbed resistance are largely compensated for by the operating efiect ofthe passages in consequence of which variations in fuelbedresistance arenot accompanied by proportionate variations in air flow, to the regionsof the fuel bed inconsistent with the actual requirements of the latter.

In Fig. 3, showing my improvement applied to a chain grate, the links 25have ribs 26 at their sides which cooperate to define passages ofvarying area in the direction of fiow, as in Fig. 1.

Also the ends of the links have ribs 21 serving the same purpose.

In Figs. 4 and 5, I show my invention as applied to a series of tuyereplates 29 of an underfeed stoker, these plates being arranged in stackedrelation and providing for the admission of air horizontallytherebetween. The air passing from a region, at l2, at higher pressureto the combustion space, at l3, at lower pressure. The horizontalpassages between adjacent tuyere plates are provided with a series oforifices and chambers to accomplish the effect already pointed out. Tothis end, referring to Fig. 5, I show the bottom side of the tuyereplate provided with a series of ribs 30, 3|, 32, and 33 which arenotched as indicated at 34, 35, 38, and 31, respectively, the notchesbeing suflicient in number and size in each'rib row to secure thedesired orifice area. With the tuyere plates in position, as shown inFig. 4, the rib rows 30, 3|, 32, and 33 rest on the fiat top surface ofthe tuyre plate immediately below, and the notches 34, .35, 36, and 31are effective as first, second, third, and fourth stage orifices tosecure the aforementioned choking efiect.

Instead of having notched ribs provided on the under surfaces of thetuyere plates, asshown in Figs. 4 and 5, each of such ribs may be madecontinuous and spaced from the top surface of the tuyere plateimmediately below, the spacing of the respective ribs being such as tosecure the desired orifice area. For-example, in Figs. 6 and 7 I showribs 38, 39, 40, and H disposed in the direction of air fiow andarranged successively closer to the top surface of the tuyere plateimmediately below so as to afford the desired first, second, third, andfourth stage orifice areas, the tuyere plates being supported inproperly spaced relation by the projections la.

' To compensate for varying fuel bed resistance, the choking effect ofthe air passages may be varied along the fuel-supporting surface, thisfeature being illustrated in Figs. 8 to 15, inclusive.

In Figs. 8 to 11, inclusive, I show grate bars of the type illustratedin Fig. 1 and having lateral ribs 42, defining orifices, or air passages.of

varying area in the direction of fiow, as already pointed out inconnection with Fig. 1; however, instead of having orifices orrestricted passage portions of uniform widths from end to end of thegrate bars, as in Fig. 1, such portions, in Figs. 8 to 11, inclusive,vary in width so as to compensate for variation in fuelbed resistance,the fiow resistance of the passages being less where the resistance ofthe fuel bed is a maximum and vice versa. To this end, it will be seenthat the ribs 42 are not continuous but are divided into a plurality. ofsections considered lengthwise of the grate bars, the sections beingshown at 42a, 42b, and 420, adjacent sections, preferably, beingseparated by mating ribs 43 and 44.

The ribs 42a define orifices 45 of maximum width, the ribs 42b defineorifices 45 of intermediate width, and the ribs 420 define orifices 41of minimum width, the orifice width depending upon the fuel bedresistance.

Obviously, with the type of stoker shown in Fig. l, the fuel bed will beof maximum depth, and, therefore, resistance, at theforward ends of thebars, this maximum fuel bed resistance being at the sections 42a wherethe width of the orifices 46 is at a maximum. The fuel bed depthdiminishes along the bars, being of inter mediate depth at the section42b where the orifices 45 are of intermediate width, and being ofminimum depth at the discharge ends of the bars, i. e., at the ribsection 420, which define the orifices 41 of minimum width.

With this modification of the rib structure on the grate bars, it willbe apparent that variation in the fuel bed resistance is compensated forby variation in passage resistance so that the tendency of air to flowexcessively through the grate where the fuel bed is thin, is minimized.

Instead of varying the orifice width from end to end on the grate bars,as in Figs. 8 to 11, inclusive, the same result may be secured byvarying the number of orificesat different sections along the bars. Tothis end, in Figs. 12 to 15, inclusive, I show grate bars having ribsections 48a, 48b, and 480 defining orifices 49a, 49b, and 490,respectively, the sections Ila being separated from the sections 481) bytransverse mating ribs 50 and sections 48!) being separated from thesections 48c by ribs 5i. As the orifices 49d, 49!), and 490 are ofuniform width, variation in reshown in Figs. 6 and '7, having lower ribsdivided into sections 53a and itbadjacent'sections being separated byribs 54, and the sections 53b being at the noses or tips of the tuyereplates. The rib sections 53a and 53b extend downwardly from the lowersides of the tuyre plates to cooperate with the upper horizontal surfaceof the next lowermost plate, as in Fig. 6. The rib sections 53a defineorifices with respect to the upper horizontal' surface of the nextlowermost plate which are wider than the orifices defined by the ribsections 531) at the tip or nose of the tuyere plate, whereby lessresistance to fiow is afforded by the rib'sections 53a than the sections53b, the fuel bed being, obviously, thicker above the lateral sections53a than above the nose or tip rib sections 53b. Also, it will beapparent'that the ribs constitute spacing supports for the tuyere plateswhen the latter are disposed in assembled stack relation.

Thev general principles of my invention may also be applied to othertypes of structures used with combustion apparatus. 1 In Fig. 17, I showa sidewall tuyere 55 incorporating my invention,

each of the air passages 56 having. one or. more chambers 51 so that theportions of the passages to either side of the chambers serve asorifices. Here again, eaclr air passage has varying areas in thedirection of flow so as to secure the effect already pointed out.

v 1 In Fig. 18, I show a modified form of sidewall sistance is securedby varying the number of orifices, the number of orifices being at amaxi mum where the fuel bed is thinnest and at a minimum where the fuelbed is thickest.

With an underfeed stoker, it is obvious that the fuel bed immediatelyabove the tips or noses of the tuyere plates is at a minimum, for, ifone views a tuyere row in the plane of the tuyeres, it will appear as aconvex surface. Accordingly, in Fig. 16, I show tuyere plates similar tothat tuyeres, where, instead of having an extensive or large castingsuch as indicated at 55 in Fig. 17, the tuyere device includesa'plurality of vertical sections or bars 58 disposed side by side. Thesections have mating ribs 55 defining orifices 60, the

orifices being separated by chambers 6i. In this form, it will beapparent that each of the air passages has varying area in the directionof fiow for the purpose already pointed out.

From the foregoing, it will be apparent that I have providedafuel-supporting or fuel-contacting surface through which air is suppliedand wherein the air passages are so formed that variation in fuel bedresistance does not cause a large difference inflow of air through thedifferent passages, that is', the passages prevent excessive flow of airto portions of the fuel bed where the fuel bed resistance is a minimum.While passages of uniform character for the entire bed are effective forthis purpose, I may modify the' passages to suitthe varying character ofthe fuel bed. For example, if the fuel bed is normaly thicker at certainregions than in others, then the orifices may be arranged to afford lessresistance to flow of air where the fuel bed is thickest and greatestresistance where the fuel bed is thinnest, the effect of the arrangementbeing that the variation in the air passages compensates for variationin fuel bed resistance. Variation in the air passages to compensate forvariation in fuel bed resistance may be secured by either varying thenumber of orifices at different sections of the fuelsupporting surface,or by varying the sizes of the orifices at different sections, or byboth.

While I have shown my invention in several forms, it wil be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various other changes and modifications, without departing from thespirit thereof, and I desire, therefore, that only such limitationsshall be placed thereupon as are imposed by the prior art or as arespecifically set forth in the appended claims.

What I claim is: I 1. In combustion ,apparatus, a grate including a aplurality of bars arranged side-by-side to provide vertical passagesbetween adjacent bars for supplying air from the space below the grateto the space thereabove,'sald bars having spaced lateral ribs extendinglongitudinally thereof, the ribs providing orifices extendinglongitudinally of the bars and the spaces between adjacent ribsproviding enlarged chambers extending longitudinally of the bars, eachpassage including a plurality of chambers and orifices with the chambersarranged between successive orifices,

2. In combustion apparatus, a grate including a plurality of barsarranged side-by-slde to provide vertical passages between adjacent barsfor supplying air from the space below the grate to the spacethereabove, said bars having spaced lateral ribsat each side andextending longitudinally thereof, similar and opposed ribs on adjacentbars forming a plurality of orifices separated by enlarged chambersformed by the spaces between adjacent ribs, whereby each passageincludes a plurality of oriflceslwith the chain '5 arranged betweensuccessive orifices.

3. In combustion apparatus, a grate providing a fuel supporting surfacehaving air admission openings and means cooperating with the grate toprovide a multiplicity of chambers arranged in series in the directionof air flow, said means and the grate providing a plurality of spacedwalls extending transversely of the direction of air fiow and definingand separating the chambers and to provide three or more spaced orificesin the v pasage between the elements, the spaces between adjacent ribsproviding expansion chambers between successlve orifices.

EARLL R. STONE.

